Liquefaction

Liquefaction is the transformation of saturated granular material from a solid state to a liquid state as a consequence of increased pore pressures that reduce the effective strength of the material (Youd, 1973). The liquefaction of a subsoil layer may induced surface disruption such as ground settlements, sand boils and lateral spreading and leads to structural damages at buildings, pipelines, bridges etc. Areas susceptible to liquefaction can be identified through detailed geologic, geomorphic and hydrologic mapping (Witter et al. 2006) while the liquefaction potential is evaluated based on data regarding the susceptibility to liquefaction of the soil layer and the expected value of ground motion triggered by the earthquake.

Studies regarding the probabilistic evaluation of liquefaction potential of the geological units in Greece started in the beginning of this decade in the Laboratory of Engineering Geology and Hydrogeology of the Department of Geology of Aristotle University of Thessaloniki. The occurrence of liquefaction phenomena and the generation of relative failures are crucial issues that should be taken into account regarding the safety of structures within an urban environment due to the seismotectonic regimen and the historical seismicity of the broader Aegean Region.

Up to day, studies of liquefaction potential at local scale have been conducted in three towns; Lefkada, Larissa and Edessa. Furthermore, the susceptibility to liquefaction of several areas in Greece is shown by Papathanassiou et al. (2005), where a map of historical liquefaction occurrences in broader Aegean region, including Greece, is compiled based on descriptions included in seismic catalogues and primary sources. The outcome provided by this study is that these types of secondary effects reoccur within specific areas in Greece particularly in Thessaly, Ionian Islands and the Gulf of Corinth including the urban environments of the town of Larissa, Aeghio and Corinth. The web site of Database of Liquefaction Occurrences in Greece (DALO) can de found in the following address http://gpapatha.weebly.com/dalo.html

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